Compact processor element for a scalable digital logic verification and emulation system

ABSTRACT

A logic simulation acceleration processor optimized for multi-value logic level simulation of electronic systems described in hardware description languages.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority under 35 USC.sctn. 119(e) from U.S. provisional patent application 60/595,057 filingdate Jun. 2, 2005 first named inventor Ganesan, titled: “Massivelyparallel platform for accelerated verification of hardware andsoftware.”

FIELD OF THE INVENTION

The present invention relates to the electronic design of integratedcircuits, and more specifically to a method for the functionalverification of a target integrated circuit design.

RELATED ART

Functional verification is one of the steps in the design of integratedcircuits. Functional verification generally refers to determiningwhether a design representing an integrated circuit performs a functionit is designed for. The inventors have previously disclosed functionalverification systems (U.S. Pat. Nos. 6,691,287, 6,629,297, 6,629,296,6,625,786, 6,480,988, 6,470,480, and 6,138,266) in which a target designis partitioned into many combinational logic blocks connected bysequential elements. The state tables corresponding to the logic blocksare evaluated and stored in multiple random access storage devices(RASDs). Such an approach may have several disadvantages. For example,evaluation of 4 state logic may require multiple cycles. Some targetdesigns may contain new language constructs such as provided by Verilog2000. Accordingly, the embodiments of previous patents may not fullyaddresses the issues of ever larger, faster, and more complex electronicsystem emulation and simulation.

Thus it can be appreciated that what is needed is a hardwareacceleration chip that provides circuit evaluation instructionprocessing in a manner that reduces the amount of time to simulate oremulate a large and complex system.

SUMMARY OF THE INVENTION

The present invention is an apparatus for processing logic evaluationinstructions compiled from a high level abstract description of anelectronic design. Typically written in a hardware description languagesuitable for synthesis, these designs are targeted for fabrication in alarge number semiconductor devices with defined functionality,performance, testability, and manufacturability in a rapid design cycle.The processor is a component of a scalable simulation system of highspeed and capacity.

Conceptually the present invention comprises electronic devices andcircuitry for reading parameterized instructions, electronic devices andcircuitry for reading a variable plurality of operands encoding digitalcircuit signal values of greater than two states, and electronic devicesand circuitry for setting a plurality of output bits to the evaluateddigital circuit signal value according to the parameterized instructionapplied to certain operands, wherein the default value of output bits atinitialization is set to the encoding denoted as UNKNOWN just as asimulator defines all wires prior to the beginning of a simulation.

The present invention addresses the growth in size and complexity ofelectronic products which exceed the capacity or useful performance ofconventional logic simulators. With arrays of the processors, a scalablesystem may contain and efficiently evaluate circuit signal values.Designers may determine in a timely manner if the design of a complexcircuit does not provide the desired functionality or contains errors oftiming or inadequate performance prior to the expense of fabricating thedesign in semiconductor manufacturing facilities. As a result electronicdesigners can bring a novel product to market sooner and at lower cost.

A BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an evaluation processor.

FIG. 2 is a portion of a truth table illustrating a 4 input 4 value XORprocessor instruction.

FIG. 3 is an embodiment in Verilog HDL of the wide variable shiftprocessor apparatus.

FIG. 4 is an embodiment in Verilog HDL of the replace range processorapparatus.

FIG. 5A-D are flowcharts of methods disclosed in the application.

DETAILED DESCRIPTION

A processor is disclosed, for evaluating circuit signal values of anelectronic design, comprising operand inputting ports for reading fouror more operands, instruction input ports for reading one or moreprocessor instructions, and encoding circuit drivers for encoding fouror more circuit signal values onto a plurality of output bits.

The processor further has a number of inputs for reading one or moreinstruction parameters, the parameter comprising a specification of theoperands to which the instruction applies. In an embodiment theprocessor can operate on up to 8 circuit signal values as inputs to asingle instruction. Conventional simulators operate on the first twovalues and then operate on a third value with the result of the priorbinary operation, as a result taking 7 cycles to accomplish theevaluation on 8 circuit signal values.

The processor further has decoding circuits for decoding four or morecircuit signal values encoded in each operand, the values comprisingUNKNOWN, TRUE, FALSE, and HIGH-IMPEDANCE whereby a logic circuit designcan be verified for errors in functionality or timing within four valuelogic simulation.

The processor further has logic AND electronic devices and circuitry forencoding the following circuit signal values when the instruction isAND:

-   -   TRUE, on the condition that all of the circuit signal values of        the operands specified by the parameter are TRUE,    -   FALSE, on the condition that any of the circuit signal values of        the operands specified by the parameter are FALSE,    -   UNKNOWN, on the condition that any of the circuit signal values        of the operands specified by the parameter are TRUE, UNKNOWN or        HIGH-IMPEDANCE but not all TRUE.

The processor further has logic NAND electronic devices and circuitryfor encoding the following circuit signal values when the instruction isNAND:

-   -   TRUE, on the condition that any of the circuit signal values of        the operands specified by the parameter are FALSE,    -   FALSE, on the condition that all of the circuit signal values of        the operands specified by the parameter are TRUE,    -   UNKNOWN, on the condition that any of the circuit signal values        of the operands specified by the parameter are TRUE, UNKNOWN or        HIGH-IMPEDANCE but not all TRUE.

The processor further has logic OR electronic devices and circuitry forencoding the following circuit signal values when the instruction is OR:

-   -   TRUE, on the condition that any of the circuit signal values of        the operands specified by the parameter are TRUE,    -   FALSE, on the condition that all of the circuit signal values of        the operands specified by the parameter are FALSE,    -   UNKNOWN, on all other combinations of circuit signal values of        the operands specified by the parameter.

The processor further has logic NOR electronic devices and circuitry forencoding the following circuit signal values when the instruction isNOR:

-   -   TRUE, on the condition that all of the circuit signal values of        the operands specified by the parameter are FALSE,    -   FALSE, on the condition that any of the circuit signal values of        the operands specified by the parameter are TRUE,    -   UNKNOWN, on all other combinations of circuit signal values of        the operands specified by the parameter.

The processor further has logic XOR electronic devices and circuitry forencoding the following circuit signal values when the instruction isXOR:

-   -   TRUE, on the condition that an odd number of the circuit signal        values of the operands specified by the parameter are TRUE and        the rest FALSE,    -   FALSE, on the condition that all of the circuit signal values of        the operands specified by the parameter are FALSE,    -   FALSE, on the condition that an even number circuit signal        values of the operands specified by the parameter are TRUE and        the rest FALSE,    -   UNKNOWN, on all other combinations of circuit signal values of        the operands specified by the parameter.

In an embodiment instructions are offered for AND, NAND, NOR, OR, andXOR for up to 8 inputs but more or fewer instruction may be offered andmore inputs can be accommodated in another embodiment of the sameinvention. In an embodiment, only two bits are utilized to encode thefour values but more bits may be optionally utilized and more values canbe optionally accommodated in another embodiment of the presentinvention.

The default value encoded on the output bits corresponds to the circuitsignal value of UNKNOWN, just as a logic simulator prior to thebeginning of simulated time or initialization has all of its nets set toUNKNOWN.

In addition to pure logic evaluation instructions, the processorsupports in native form certain instructions such as wide variable shiftavailable in hardware description languages such as Verilog. Rather thanperforming the atomic steps in shifting data through a register, theprocessor has electronic devices and circuitry means for reading aninput vector OLD, electronic devices and circuitry means for reading aplurality of scalars SHIFT, XOUT, executing means for executing a widevariable shift instruction comprising electronic devices and circuitrymeans for replicating the scalar XOUT to the width of the processoroutput vector OUT; electronic devices and circuitry means for shiftingthe input vector OLD to the right according to the binary value SHIFT;electronic devices and circuitry means for bit-wise OR operation of theshifted OLD vector with the replicated XOUT vector, electronic devicesand circuitry means for assigning the result of the vector OR operationto the processor output vector OUT.

Another such instruction is Replace-Range. The processor further hasinput port electronic devices and circuitry means for reading an inputvector NEW, electronic devices and circuitry means for reading aplurality of input scalars ENABLE, WIDTH, and scratchpad storage forstoring a variable RSHAMT, and shift register or multiplexor circuits toexecute a replace range instruction by shifting the input vector NEW tothe left according to the decimal value SHIFT on the condition that bit0 of ENABLE is true; shift register or multiplexor circuits to shift theinput vector NEW to the right according to the decimal value RSHAMTassigned to be 32 minus SHIFT; multiplexor means for replacing some partof OLD with lower “WIDTH” plus 1 vector members of shifted vector NEW, acircuit tree for translating a decimal value of WIDTH to a binary mask,a multiplexor for assigning a replacement mask from a left shifted maskon the condition that the 0 bit of ENABLE is true, assigning from aright shifted mask if the 1 bit of ENABLE is true and the right shiftamount RSHAMT is non zero, and assigning all bits to be zero ifotherwise, means for replacing some part of OLD with lower “WIDTH” plus1 vector members of NEW shifted left if 0th bit of enable is true orshifted right by 32 minus shift if 0th bit of enable is false andbit-wise OR'ing the resulting combination of OLD and NEW with the resultof replicated XOUT.

In the event that inputs require greater than 64 bit inputs theembodiment of the processor uses a method, the method comprising:generating a plurality of wide variable shift instructions and aplurality of replace range instructions, padding the most significantinput bits with zeros to fit the available input width, applying theinstructions to overlapping or to contiguous members of the circuitsignal value vectors, assigning the instructions to a plurality ofprocessors, storing intermediate values and ORing the results.

Such processors disclosed in the present invention may be customdesigned electronic devices but for economies are more likely programmedonto an existing array of logic cells or logic gates. Thus theinterconnection among an underlayment of logic gates may be read from acomputer readable medium and device programmed in a variety of ways.These methods of programming an electronic device to perform evaluationprocessor operations comprises one or more of the following steps:making fuses or anti-fuses conductive or non-conductive, injectingcharge to floating gates, storing a binary pattern on a computerreadable medium, applying current or voltage to a memory controlling apass transistor, and recording a tape to define an image of conductiveor non-conductive traces or polygons in a mask, the method furthercomprises but is not limited to the steps of configuring an electronicdevice to read one or more instructions selected from the group ofinstructions following: AND, OR, NAND, NOR, XOR; configuring anelectronic device to read a plurality of operands which represent inputcircuit signal values selected from the group following: UNKNOWN, TRUE,FALSE, HIGH-IMPEDANCE; configuring an electronic device to encode on aplurality of output bits the circuit signal values which result fromapplying said instruction to said plurality of operands, wherein theplurality of operands simultaneously read and evaluated in one step arefour or more, and wherein the plurality of circuit signal values read orencoded in one step are four or more.

An article of manufacture is disclosed comprising a computer readablemedium on which is encoded the computer implementable steps forprogramming an electronic device to perform evaluation processoroperations, the steps comprising the method of the present invention. Acomputer program product is disclosed for producing masks, fuse maps,charge storage or files for configuring gate arrays, programmable logicdevices, or semicustom integrated circuits which perform the presentinvention.

1. A processor, for evaluating circuit signal values of an electronicdesign, comprising operand inputting electronic devices and circuitryfor reading four or more operands, instruction input electronic devicesand circuitry for reading one or more processor instructions, andencoding electronic devices and circuitry for encoding four or morecircuit signal values onto a plurality of output bits, the processorfurther comprising electronic devices and circuitry for reading an inputvector OLD, electronic devices and circuitry for reading a plurality ofscalars SHIFT, XOUT, executing electronic devices and circuitry forexecuting a wide variable shift instruction comprising electronicdevices and circuitry for replicating the scalar XOUT to the width ofthe processor output vector OUT; electronic devices and circuitry forshifting the input vector OLD to the right according to the binary valueSHIFT; electronic devices and circuitry for bit-wise OR operation of theshifted OLD vector with the replicated XOUT vector, electronic devicesand circuitry for assigning the result of the vector OR operation to theprocessor output vector OUT further comprising electronic devices andcircuitry for reading an input vector NEW, electronic devices andcircuitry for reading a plurality of input scalars ENABLE, WIDTH, andstoring electronic devices and circuitry for storing a variable RSHAMT,executing electronic devices and circuitry for executing a replace rangeinstruction by shifting the input vector NEW to the left according tothe decimal value SHIFT on the condition that bit 0 of ENABLE is true;electronic devices and circuitry for shifting the input vector NEW tothe right according to the decimal value RSHAMT assigned to be 32 minusSHIFT; electronic devices and circuitry for replacing some part of OLDwith lower “WIDTH” plus 1 vector members of shifted vector NEW,electronic devices and circuitry for translating a decimal value ofWIDTH to a binary mask, electronic devices and circuitry for assigning areplacement mask from a left shifted mask on the condition that the 0bit of ENABLE is true, assigning from a right shifted mask if the 1 bitof ENABLE is true and the right shift amount RSHAMT is non zero, andassigning all bits to be zero if otherwise, electronic devices andcircuitry for replacing some part of OLD with lower “WIDTH” plus 1vector members of NEW shifted left if 0th bit of enable is true orshifted right by 32 minus shift if 0th bit of enable is false andbit-wise OR'ing the resulting combination of OLD and NEW with the resultof replicated XOUT.
 2. A method of programming an electronic device toperform evaluation processor operations wherein programming comprisesone or more of the steps comprising the group: making fuses oranti-fuses conductive or non-conductive, injecting charge to floatinggates, storing a binary pattern on a computer readable medium, applyingcurrent or voltage to a memory controlling a pass transistor, andrecording a tape to define an image of conductive or non-conductivetraces or polygons in a mask, the method comprising the steps ofconfiguring an electronic device to read an input vector OLD, read aplurality of scalars SHIFT, XOUT, execute a wide variable shiftinstruction, replicate the scalar XOUT to the width of the processoroutput vector OUT; shift the input vector OLD to the right according tothe binary shift value SHIFT; bit-wise OR operation of the shifted OLDvector with the replicated XOUT vector, assign the result of the vectorOR operation to the processor output vector OUT, and read a plurality ofinput scalars ENABLE, WIDTH, and store a variable RSHAMT, execute areplace range instruction by shifting the input vector NEW to the leftaccording to the decimal value SHIFT on the condition that bit 0 ofENABLE is true; shift the input vector NEW to the right according to thedecimal value RSHAMT assigned to be 32 minus SHIFT; replace some part ofOLD with lower “WIDTH” plus 1 vector members of shifted vector NEW,translate a decimal value of WIDTH to a binary mask, assign areplacement mask from a left shifted mask on the condition that the 0bit of ENABLE is true and the right shift amount RSHAMT is non-zero, andassigning all bits to be zero if otherwise, replace some part of OLDwith lower “WIDTH” plus 1 vector members of NEW shifted left if 0^(th)bit of enable is true or shifted right by 32 minus SHIFT if 0^(th) bitof ENABLE is false and bit-wise OR the resulting combination of OLD andNEW with the result of replicated XOUT and to read at least oneinstruction selected from the group of instructions following: AND, OR,NAND, NOR, XOR; configuring an electronic device to read a plurality ofoperands which represent input circuit signal values selected from thegroup following: UNKNOWN, TRUE, FALSE, HIGH-IMPEDANCE; configuring anelectronic device to encode on a plurality of output bits the circuitsignal values which result from applying said instruction to saidplurality of operands, wherein the plurality of operands simultaneouslyread and evaluated in one step are four or more, and wherein theplurality of circuit signal values read or encoded in one step are fouror more.
 3. An article of manufacture comprising a program producttangibly embodied on a computer readable medium to effect theprogramming of an electronic device to perform evaluation processoroperations, the steps comprising: configuring an electronic device toread an input vector OLD, read a plurality of scalars SHIFT, XOUT,execute a wide variable shift instruction, replicate the scalar XOUT tothe width of the processor output vector OUT; shift the input vector OLDto the right according to the binary shift value SHIFT; bit-wise ORoperation of the shifted OLD vector with the replicated XOUT vector,assign the result of the vector OR operation to the processor outputvector OUT, and read a plurality of input scalars ENABLE, WIDTH, andstore a variable RSHAMT, execute a replace range instruction by shiftingthe input vector NEW to the left according to the decimal value SHIFT onthe condition that bit 0 of ENABLE is true; shift the input vector NEWto the right according to the decimal value RSHAMT assigned to be 32minus SHIFT; replace some part of OLD with lower “WIDTH” plus 1 vectormembers of shifted vector NEW, translate a decimal value of WIDTH to abinary mask, assign a replacement mask from a left shifted mask on thecondition that the 0 bit of ENABLE is true and the right shift amountRSHAMT is non-zero, and assigning all bits to be zero if otherwise,replace some part of OLD with lower “WIDTH” plus 1 vector members of NEWshifted left if 0^(th) bit of enable is true or shifted right by 32minus SHIFT if 0^(th) bit of ENABLE is false and bit-wise OR theresulting combination of OLD and NEW with the result of replicated XOUTand to read one or more instructions selected from the group ofinstructions following: AND, OR, NAND, NOR, XOR; configuring anelectronic device to read a plurality of operands which represent inputcircuit signal values selected from the group following: UNKNOWN, TRUE,FALSE, HIGH-IMPEDANCE; configuring an electronic device to encode on aplurality of output bits the circuit signal value which result fromapplying said instruction to said plurality of operands, wherein theplurality of operands simultaneously read and evaluated in one step arefour or more, and wherein the plurality of circuit signal values read orencoded in one step comprise four or more distinguishable values.